each drawer is an individual unit and you can stack as many as you like. in these units in particular there is actually a much smaller gap above the drawers compared to other drawer units in which there is quite a large gap, and since they are completely enclosed as opposed to just a frame in which the drawer sits they are much more secure. however, i can fit my finger through the gap so i am sure that a crested gecko or any snake would be sure to wedge itself through the gap and find a way out of the unit. i have yet to find any kind of drawer unit that would work for arboreal geckos or snakes just because they aren't secure enough. these are the best i've found, but still only good for terrestrial species that won't be able to reach that gap in the top to escape.

i'll post some pics of the inhabited cages tonight.